The present invention relates to a diaphragm for a loud speaker.
In order to prevent a fire, flame-retarding treatment of various components not only in electrical equipment but also in acoustic equipment is required. Therefore, flame-retarding of speakers is also required. In conventional flame-retarded speakers, a flame-retarding coating is formed upon the surface of a diaphragm made of natural or synthetic fibers or formed by molding a synthetic resin. Consequently, the mass of such speaker diaphragm is inevitably increased, resulting in a decrease in acoustic pressure and in the degradation of the better physical properties of the original diaphragm. Thus, the acoustic characteristics of the speaker are considerably degraded.
It is well known that salts of phosphoric acid, especially ammonium phosphate, is a preferred inorganic flame retarder for cellulose, but ammonium phosphate has high hygroscopic property, and strongly attacks metals, especially copper. Moreover, it is difficult to apply ammonium phosphate to cellulose, and ammonium phosphate gives rise to the growth of mold.
The organic flame retarders containing halogens and phosphorus are very expensive in general and have a fatal defect in that smoke is produced when the articles treated with such a flame retarder are exposed to fire.